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Picat 逻辑编程语言简介

Combinatorial Search With Picat

Picat is a simple, and yet powerful, logic-based multi-paradigm programming language aimed for general-purpose applications. Picat is a rule-based language, in which predicates, functions, and actors are defined with pattern-matching rules. Picat incorporates many declarative language features for better productivity of software development, including explicit non-determinism, explicit unification, functions, list comprehensions, constraints, and tabling. Picat also provides imperative language constructs, such as assignments and loops, for programming everyday things. The Picat implementation, which is based on a well-designed virtual machine and incorporates a memory manager that garbage-collects and expands the stacks and data areas when needed, is efficient and scalable. Picat can be used for not only symbolic computations, which is a traditional application domain of declarative languages, but also for scripting and modeling tasks.

Logic programming has made great strides in solving combinatorial search problems, as witnessed by the cultivation of CLP, ASP, and tabled Prolog systems. Picat, a new member of this family, follows a different doctrine than Prolog in offering the core logic programming concepts: arrays and maps as basic data types; implicit pattern matching with explicit unification and explicit non-determinism; functions that are easier to use than relations for deterministic computations; loops that are more convenient than recursion for scripting and modeling purposes. Picat provides facilities for solving combinatorial search problems, including a common interface with CP, SAT, and MIP solvers, tabling for dynamic programming, and a module for planning. Picat's planner module, which is implemented by use of tabling, has produced surprising and encouraging results; thanks to term-sharing and resource-bounded tabled search, it overwhelmingly outperforms the cutting-edge ASP and PDDL planners on several planning benchmarks used in recent ASP and IPC competitions.